GMC T Series 1994 Repair Manual page 342

4. Valves.
NOTICE:
Avoid breaking the valve guide. If the
valve stem has mushroomed, remove burrs by
chamfering the valve stem with an oil stone or
file. Do not remove the valve from the guide
using a hammer and drift punch.
5. Spark plugs.
Inspect
Threaded plugs.
Cup plugs, if damaged or leaking, replace them.
E3
Remove or Disconnect
1. Obtain a suitable self-threading screw.
2. Drill a hole in the plug.
3. Install the self-threading screw.
4. Pry out plug.
Cylinder head gasket and mating surfaces for
leaks, corrosion and blow-by. If the gasket has
failed, determine the cause:
- Improper installation.
- Loose or warped cylinder head.
- Missing or damaged dowel pins.
IJJi Clean
• Cylinder head bolts.
• Cylinder head. Carefully remove all varnish, soot
and carbon.
DO NO T
• Valve guides, refer to Figure 36.
• Threaded holes.
• Remains of sealer from plug holes.
Inspect
1. Cylinder head bolts for damaged threads, and
damaged cylinder heads caused by improper use
of tools.
Important
• Do not attempt to weld the cylinder head,
replace it.
2. Cylinder head deck, intake, and exhaust manifold
mating surfaces for flatness, refer to Figure 37.
These surfaces may be reconditioned by parallel
grinding. If more than 0.25 mm (0.010 in.) must
be removed, replace the head.
3. All threaded holes for damage. Threads may be
reconditioned with
" Thread Repair" in this section.
4. Sealing surfaces, including water jacket plugs
(if they have been removed).
VALVE GUIDE SERVICE
Tools Required:
J 8101 Valve Guide Cleaner
use a motorized wire brush.
thread inserts, refer to
Figure 35 - Valves, Valve Seals, and Valve Springs
VALVE GUIDE
CLEANER
BT-6415
OR
J— 8101
G34358— 6A-BG-EDS